Leg foundation for skeleton towers.



' PATENTED JULY 30, 1907.

R. L. ALLEN. LEG FOUNDATION FOR SKELETON TOWERS.

APPLICATION FILED MAY 26, 1905.

2 SHEETS-SHEET 1.

IN VENT)?! zap/M2 04 TTHHNEK rd! nonms PETERS co., WASHINGTON. 0. c4

.PATENTED JULY 30, 1907.

I R. L. ALLEN. LEG FOUNDATION EoE. SKELETON TOWERS.

APPLIOATION FILED MAY 25, 1906.

2 SHEETS-SHEET 2.

WITNESSES,

' arrow Ev. l

co.. \vAsmncnm. n. c.

rn s-nomzls PETERS UNITED STATES PATENT FFIQ.

ROBERT L. ALLEN, OF SYRACUSE, NEW YORK, ASSIGNOR TO AROHBOLD-BRADY COMPANY, OF SYRACUSE, NEW YORK, A CORPORATION OF NEW YORK.

LEG FOUNDATION FOR SKELETON TOWERS.

Specification of Letters Patent.

Patented July 30, 1907.

Application filed May 25, 1905. Serial No. 262,297.

To all whom it may concern:

Be it. known that I, ROBERT L. ALLEN, of Syracuse, in the county of Onondaga, in the State of New York, have invented new and useful Improvements in Leg Foundations for Skeleton Towers, of which the following, taken in connection with the accompanying drawings, is a full, clear, and exact description.

This invention relates to improvements in concrete foundations or anchorage for the individual legs of skeleton tower structures, the specific object of which is to resist both the downward thrust and upward pull to which the tower legs are subjected. These towers are usually supported upon a series of upright legs which are spaced apart over a comparatively large area at the base, but converge upwardly so as to closely approach each other at the top and are braced or tied together at intervals in such manner as to form a truss structure in which the load and strains are evenly distributed and concentrated in a line with the center of gravity of the tower. Under such a construction each leg is subjected to a lifting and compression strain and the strain upon the foundation is, therefore, axial of the leg which is supported upon said foundation, as distinguished from lateral strain. I have, therefore, sought in my present invention to construct and adapt a foundation for each leg tomore positively resist such upward lift or downward thrust, and to this end I provide each leg with a pyramidal concrete foundation which is embedded in the earth with its axis substantially co-incident with the axis of the leg which is supported thereon, each pyramoid having a broadened horizontal footing or base of the sam material integral therewith and extending under the superimposed earth which surrounds the pyramoid, thereby increasing the resistance to lifting, or a downward thrust of the tower leg, it being understood that each oweileg is securely anchored tothe base or footing of the concrete pier.

A further object is to embed a suitable bond, such as a wire fabric, or equivalent into the broadened base or footing of the pier, such bond being preferably co-extensive with the area of such footing to more evenly distribute the lifting and down-thrust strain to which the pier or foundation of each leg may be subjected.

A still further object is to embed anchor-plates in the footing of the pier equidistant from the axial line of the pier and at opposite sides thereof below the bond and to firmly tie the lower end of the leg to these anchor-plates and to associate them with the structure of the pier so that the u nitaiy foundation constitutes a truss, or rather the equivalent of a truss structure in its resisting power to the lifting and compression strains to which it is subjected Other objects and uses will be manifest from the following description.

In the drawings, Figures 1 and 2 are face views of my improved tower-leg foundation taken at right angles to each other, a portion of the concrete being broken away in Fig. l, to show one of the anchor rods, and a portion of the woven wire bond in the base of the pier, which is also shown by breaking away a portion of the base in Fig. 2. Figs. 3 and 4 are respectively an elevation and a top plan of a tower mounted upon my improved foundations.

In entering upon a description of this tower foundation, it must be borne in mind that the conditions of a skeleton tower structure are vastly different from an ordinary post or pole for the reason that the tower structure is built in the form of a truss in which the strain upon each leg is up or down, while in a pole, or p ost, the strain is lateral'only.

, In other words, in considering the merits of my invention, the distinction must be made as between a truss-structure and a beam-structure, the tower corresponding to the truss and the pole or post corresponding to a beam. My invention, therefore, is specially adapted for skeleton-tower-structure and not for supporting a pole or post, and consists essentially of a pyramoid 1 of concrete and a footing 2 of the same material integral with the base of the pier and in which is embedded a bond 3-* of woven wire or equivalent structure. This pyramoid and its footing constitutes a unitary concrete foundation which is embedded to a considerable depth in the earth with its upper end protruding slightly above the surface of the ground for receiving and supporting a suitable bed-plate -4 in which is firmly anchored the lower end of a tower-leg 5-.

It will be observed upon reference to Fig. 1, that the tower-leg is disposed in an inclined position, this being the usual angle of one of the legs of a tripod-skeletontower-structure, and it will also be observed that the axis of the pyramoid lis substantially co-incident with the axis of the tower-leg -5, such axis being, therefore, inclined in one direction from a vertical line and the base of the pyramoid is broadened in the direction of such inclination so that the inner and outer sides of the pier converge upwardly from the base, the outer upright face being disposed at a greater angle from a vertical line than the inner side, while the other faces of the pyramoid are substantially vertical or parallel, as seen in Fig. 2. The footing -2 extends laterally some distance from all sides of the base of the pier l, its upper face being substantially flat or horizontal and forms a sharp angle with the sides of the pier in order to avoid as far as practicable any wedging action during the upward lifting strains upon the pier.

The lower face of the footing 2 is preferably rounding or convex in one direction, usually across its narrow width for the purpose of increasing the resistance area against downward thrust, the horizontal upper face together with the inclined inner and outer faces affording ample resistance area to resist upward lift of the pier.

In order to further increase the resisting power against upward lift I provide the footing 2 with a fabric or other metal bond 3 which is embedded into the concrete and is preferably convexed upwardly intermediate its ends to afford as broad a resisting area as possible acting against the superimposed earth and also serving to bind the concrete together at the junction of the pyramoid with its footing. These foundations or piers 1 are elongated radially with reference to the vertical axis of the tower or in the direction of inclination pf the legs -5 and the inner and outer faces previously referred to indicate respectively the sides nearest to and most remote from the axis of the tower and may be regarded as having such significance in the subsequent description. Each of these piers or foundations 1 is provided with a pair of tie-bolts or rods 6 extending upwardly from points below the metal bond -3- parallel with the inher and outer side faces of the pyramoid land have their upper ends securely anchored to suitable ears 7 on the plate 4 which rests upon the top face of the pier 1. These tie-rods are embedded in the concrete of the pyramoid and its footing andtheir lower ends are'firmly secured to anchor plates 8 which are embedded in the footing 2 below the bond 3-, such plates being substantially flat and disposed at right angles to their respective tie-rods so that when the nuts upon the upper ends of the bolts or rod 6 are drawn up tightly the anchor-plate 4 and its tower-leg 5 become practically unitary parts of the pier structure. In building these piers or foundations the earth is excavated at suitable points corresponding to the position of the tower legs and such excavation are then partially filled with concrete,

which concrete is built up in the forms seen in Figs.

1 and 2, it being understood that the metal bond 3-, anchor-plates -8- and tie-rods 6 are embedded in the concrete as the piers or foundations are built up, after which the earth is replaced and firmly packed upon the footing 2 and around the greater body of the pyramoid 1- or preferably the portion of the earth receiving the base or footing 2 is undercut under the solid earth so as to afford greater resistance to the uplift of the pier leaving the upper ends of the pier protruding slightly above the ground for the reception of the plates 4 and ends of the legs 5-, which latter are usually expanded in tapering sockets in the bed-plates 4-'-.

In Figs. 1 and 2 I have shown a plurality of, in this instance three, piers spaced equidistant apart around a common center and have shown the axes of the legs which are mounted upon these piers, as converging upwardly in lines co-incident with the axes of their respective piers so that the lower ends of the sides of the pyramoid are equidistant from their respective axes. The inner and outer tapering sides of the pier nearest to and most remote from the axis of the tower are disposed at different angles with reference to a vertical line, the outer side farthest from the axis of the tower inclining upwardly and inwardly at a greater angle than the inner side so as to afford a greater area to resist uplift of the pier when the lateral strain is applied to the same side of the tower. These lateral strains upon the tower may be produced from various causes, such as wind pressure or undue tensioning of a wire or other power which may tend to draw the tower laterally in one direction or another, and under such conditions the lower end of the axis of one or more of the piers becomes a fulcrum upon which the tower is inclined to tilt in the direction of the strain, thus producing an uplift upon one or more of the opposite piers, and it is this uplift which I am particularly desirous to prevent and the structure of the pier is made to carry out this purpose, which as previously stated, is accomplished by three essential features of construction, viz: first, arranging the axes of the piers in a line with the axes of their respective upwardly converging legs which they support and which are tied to the piers.

Second, making the outer side farthest from the vertical axis of the tower at a greater angle than the inner side so as to increase the area bearing against the earth at such side, and third, to extend the footing beyond the sides of the pyramoid part of the pier to produce substantially flat horizontal upper faces underlying the superimposed earth, thereby affording additional and more effective resistance to the uplift, the strain produced upon the projecting parts of the flat footing being distributed across the entire footing by means of a bond 3 and tie-rods 6 which are anchored below the bond.

Having thus described my invention, what I claim is:

A leg foundation for skeleton towers comprising a concrete pier having a broadened footing or base, the upper face of which is disposed in a substantially horizontal plane projecting from all sides 0 the superposed body of the pier, a metal bond in the footing below said horizontal face and extending under the upright sides of the superposed portion of the pier to resist sheering strains on the footing, reinforcing rods embedded in the piers near their inner and outer faces and having their lower ends anchored in the footing below said bond and their upper ends extending; through and beyond the top of the pier, a tower leg rising from the top of the pier, and means for connecting the tower legto the upper ends of the reinforcing rods.

In witness whereof I have hereunto set my hand this 19 day of May 1905.

ROBERT L. ALLEN.

Witnesses MILDRED M. No'r'r, HowAnD I. DENISON. 

